8 Tuberculosis infection prevention and control
Take the chapter quiz before and after you read this chapter.
First time? Register for free. Just enter your email or cell number and create a password.
- Tuberculosis in low-resource settings
- Tuberculosis transmission
- Diagnosis of tuberculosis
- Drug-resistant tuberculosis
- Global tuberculosis control
- Tuberculosis infection prevention and control (TB-IPC)
- Administrative control measures
- Environmental control measures
- Respiratory protection control measures
- Healthcare worker adherence to tuberculosis control measures
- Occupational health services for tuberculosis
- Tuberculosis prevention in the community
- Case studies
When you have completed this chapter you should:
- Understand how tuberculosis (TB) affects low-resource settings
- Understand which forms of TB pose a risk for TB transmission
- Be familiar with diagnostic tests for TB
- Know about the WHO 3I’s strategy for TB control
- Be familiar with the hierarchy of controls for prevention of TB transmission
- Know how to reduce the risk of TB transmission in healthcare facilities
- Know how to reduce the risk of TB transmission in households and communities
- Understand the influence of healthcare worker behaviour on compliance with TB prevention measures
- Be familiar with policies and surveillance for TB among health-care workers
- Be aware of the challenges posed by TB-infection prevention and control (TB-IPC) in low-resource settings.
Tuberculosis in low-resource settings
8-1 What is tuberculosis?
Tuberculosis (TB) is caused by a bacterial pathogen called Mycobacterium tuberculosis (the TB bacillus). In most people, TB affects their lungs. However, almost any bodily organ can be affected by TB, e.g. brain, spine, kidneys.
8-2 How is tuberculosis spread?
TB infection is spread to others mainly by the airborne route. Coughing releases the TB bacilli into the air from the lungs of an infected person. This TB-contaminated air can then be breathed in by others, who may go on to develop TB infection and/or disease.
Tuberculosis infection is spread by the airborne route.
8-3 What is the natural history of tuberculosis?
About one third of the world’s population are infected with TB bacilli. They have a condition known as latent TB infection (LTBI). In latent TB infection, a person has been exposed to and infected with TB bacilli, but there are very few TB bacilli in their lungs. As long as their immune system (body’s defences against infection) remains intact, the TB infection can be controlled and the TB bacilli are prevented from multiplying. In people whose immune system is underdeveloped (infants) or weakened (HIV, diabetes, malnutrition), the latent TB infection can progress to TB disease (i.e. tuberculosis). This happens when the body’s immune system is no longer able to contain the multiplying TB bacilli. The TB bacilli can then cause TB disease (tuberculosis) in the lungs or can spread via the lymph nodes or via the bloodstream to cause disease in other organ systems, e.g. abdomen, central nervous system. Most people with TB infection will never develop TB disease (tuberculosis).
About one third of the world’s population have latent tuberculosis infection (LTBI).
8-4 Who is at risk for acquiring tuberculosis?
Anyone who is exposed to TB (in close contact with an infectious TB case) can develop latent TB infection. For a person with latent TB infection, the lifetime risk of progressing to TB disease is about 10%. In people living with HIV, the risk of developing TB disease is much higher (up to 10% per year.) This risk can be reduced by ensuring HIV-infected people have access to antiretroviral treatment, which may partially restore the function of the immune system. Other well-recognised risk factors for TB disease include extremes of age (young infants and the elderly), diabetes, steroids or cancer chemotherapy (which weaken the immune system), smoking and malnutrition.
In people living with HIV the risk of developing tuberculosis disease is up to 10% per year.
8-5 What is the global burden of disease caused by tuberculosis?
Although TB occurs globally, over 90% of TB disease is diagnosed in people living in low-middle income countries. About 9 million people are newly diagnosed worldwide with TB each year. The highest number of new TB cases are from countries in Asia and Africa. TB patients are often co-infected with HIV (14% worldwide, but up to 60% co-infection rates reported in some African countries). Worldwide, TB causes about 1.5 million deaths per year and is the second largest killer from a single infectious pathogen after HIV/AIDS.
8-6 What forms of tuberculosis pose the greatest risk for transmission of disease?
People with pulmonary (lung) TB or laryngeal (throat) TB pose the greatest risk of transmission to others. TB is spread by the airborne route. When TB-diseased people cough they produce infectious ‘TB droplet nuclei’ or cough aerosols. These are tiny particles containing TB bacilli which may be suspended in the air for minutes to hours (in the absence of ventilation or air movement).
Pulmonary and laryngeal (throat) tuberculosis are the most infectious forms of disease.
8-7 When are tuberculosis patients most infectious?
People with undiagnosed pulmonary TB and those who have recently started treatment (less than two weeks) are most infectious. A person with untreated pulmonary TB can infect many people within their social and work environment. Once effective TB treatment is started, the number of live TB bacilli in the person’s cough aerosols drop dramatically, making them less infectious. This is why early identification of people with TB disease is so important to reduce TB transmission.
Other factors associated with infectiousness include:
- Cough (in patients with TB of the lungs and larynx)
- Lung cavities (which are filled with TB bacilli)
- Sputum smear positive TB (acid-fast TB bacilli on smear microscopy)
- Sputum culture positive for TB
- Patients undergoing procedures that may cause coughing (see below).
People with undiagnosed or newly diagnosed pulmonary tuberculosis are the most infectious.
8-8 When is tuberculosis transmitted?
TB can be transmitted whenever a person with TB disease of the lungs or throat coughs, shouts or sneezes (i.e. whenever there is forcible exit of air from the respiratory tract). In the healthcare setting, TB exposures occur most commonly when:
- Many people congregate in confined spaces with poor air flow, e.g. waiting areas or corridors outside consultation rooms.
- Exposure of healthcare workers to TB can occur during procedures such as sputum collection, nebulisation, suctioning, intubation, extubation and bronchoscopy.
- Infectious TB patients (diagnosed or undiagnosed) who are hospitalised also pose a hazard of TB transmission to fellow patients and staff if not appropriately isolated.
8-9 What factors influence the risk of tuberculosis transmission?
The two main factors that determine the risk of TB transmission are:
- The duration of exposure (how long)
- The degree of exposure (how much).
The longer one remains in close contact with an infectious TB case, the greater the chance that you will acquire TB. The degree of exposure is determined by many factors, e.g. the number of live TB bacilli in the air; the number of TB source cases in the room/ward; the infectiousness of the TB source case/s and how frequently the air in the environment/room/ward is exchanged (adequacy of ventilation.)
The risk of transmission is determined by the duration and degree of tuberculosis exposure.
8-10 Which areas in healthcare facilities have the highest risk for tuberculosis transmission?
In primary care clinics or community health centres, areas with high risk for TB transmission are waiting rooms, HIV clinics and sputum collection areas. In hospitals, adult medical wards, radiology departments, TB laboratories and paediatric wards are considered high-risk areas. In addition, any areas where aerosol-generating procedures occur (resuscitations, intubations, bronchoscopy areas) may be at higher risk for TB exposures to staff and other patients.
8-11 When are patients with tuberculosis considered to be non-infectious?
For patients not yet on anti-TB treatment, the following factors would make them less infectious:
- No coughing
- No lung cavities
- TB outside of the lungs (extra-pulmonary TB)
- Sputum smear negative for TB (no acid-fast bacilli on smear microscopy)
- Sputum culture negative for TB.
For patients who have started anti-TB treatment, the following criteria can be used to identify those who are no longer infectious (and could be safely de-isolated):
- At least two consecutive sputum smear microscopy samples negative for TB (sputum is usually submitted for repeat smear and culture after two months of treatment) AND
- Evidence of clinical improvement (resolution of cough/fever) AND
- Adherence to an adequate anti-TB treatment regimen for two weeks or more.
Diagnosis of tuberculosis
8-12 When should the diagnosis of tuberculosis be suspected?
Pulmonary TB is the most common form of TB disease. Symptoms of pulmonary TB can include any or all of the following:
- A chronic cough (more than two weeks)
- Unintentional weight loss
- Night sweats
- Loss of appetite
- Chest pain
- Coughing up blood (haemoptysis)
- Failure of the respiratory symptoms to improve after an appropriate course of antibiotics.
TB in other organs can cause some of the above symptoms (fever, night sweats, weight loss) but in addition usually causes symptoms related to the organ system involved. For example, TB meningitis may cause symptoms like headache, confusion or decreased level of consciousness.
8-13 How is tuberculosis usually diagnosed?
In many low-resource settings, a method called sputum smear microscopy is still the main or only method used to diagnose TB. A microscope is used to magnify a sample of sputum placed on a glass slide. A trained laboratory technician stains the sputum with various dyes that make it easier to see the acid-fast TB bacilli. Usually two to three sputum samples per patient are examined. A patient whose sputum contains TB bacilli is said to be ‘smear-positive’ for TB. The degree of infectiousness of a patient can also be estimated by counting the number of TB bacilli (called AFBs or acid-fast bacilli) under the microscopy field, e.g. grade 1, 2 or 3 smear positive. Although sputum microscopy can provide a quick diagnosis, the test does not detect patients with very few TB bacilli (pauci-bacillary disease), cannot differentiate easily other types of mycobacteria and cannot give any indication of TB drug-resistance.
Although sputum TB microscopy is widely available, it cannot detect all patients with tuberculosis or give any indication of drug-resistance.
8-14 What other tests are available to confirm the diagnosis of tuberculosis?
In very low-resource settings, TB smear microscopy may be the only laboratory diagnostic test available. Where a TB reference laboratory exists, TB smear microscopy is usually followed by TB culture. This process involves introducing the patient’s sputum sample (which may contain TB bacilli) onto a solid or into a liquid growth medium to support potential growth of TB under laboratory conditions. After between one to six weeks (depending on the type of growth medium used), the culture may become positive.
Further testing of the cultured bacilli allows the laboratory to confirm that the TB bacilli grown belong to the Mycobacterium tuberculosis complex (rather than other strains of mycobacteria). Additional testing can then be done to check for the anti-TB drug susceptibility of the strain (see below.) All of these tests are significantly more expensive and time-consuming than TB microscopy and require specialised equipment, highly trained laboratory staff and reliable access to water and electricity.
A new molecular test (GeneXpert or Xpert® MTB/RIF) has been made available in many countries to allow for rapid (less than two hours), point-of-care (on-site) testing for TB bacilli in sputum. This test can simultaneously detect the presence of TB DNA, as well as mutations in the gene that determine the TB bacilli’s susceptibility to the anti-TB drug, rifampicin. The significance of this new test is that the TB diagnosis can be confirmed at the same visit. Even more importantly, drug-resistant TB (see below) can be identified at initial TB diagnosis (as compared with traditional testing methods for drug-resistant TB which take weeks to months, allowing a prolonged time for onward TB transmission).
A new molecular test (Xpert® MTB/RIF) can deliver rapid, on-site testing for tuberculosis and tuberculosis drug-resistance.
8-15 What is drug-susceptibility testing (DST) for tuberculosis?
Drug susceptibility (sensitivity) testing is done to determine if an individual patient’s strain of TB bacilli will be effectively treated by the standard first-line, or in some cases by second-line anti-TB drugs. The drug susceptibility of a particular TB strain can be tested by observing growth of TB bacilli in the presence of different anti-TB drugs, or using special techniques that identify mutations (changes) in the genes related to drug action.
8-16 What is drug-resistant tuberculosis?
Drug resistance develops when the standard drugs used to treat TB become less effective in killing the TB bacilli. Drug resistance can develop when TB patients stop taking their medication or take it infrequently (acquired resistance). However, drug-resistant TB (DR-TB) can also be transmitted directly (primary resistance). This happens when a person is directly infected with a resistant form of TB through contact/exposure to someone with DR-TB.
8-17 Why is drug-resistant tuberculosis a problem?
Drug-resistant TB is much more difficult and expensive to treat than normal, drug-susceptible (sensitive) TB. This is because in DR-TB the most powerful anti-TB drugs have become ineffective through development of drug resistance. This means that DR-TB has to be treated with inferior drugs, that are less powerful at killing TB and often have many side-effects. To counteract for the fact that these drugs are less effective, more drug combinations are used (up to six different drugs). The DR-TB regimens also have to be given for much longer than the standard six-month TB regimen (for 24 months or longer).
Drug-resistant tuberculosis is much more difficult and expensive to treat.
8-18 How does tuberculosis become drug-resistant?
Drug-resistant TB can be acquired during the course of TB therapy under the following circumstances:
- When the full course of treatment is not completed (treatment defaulters)
- When patients take treatment infrequently (poor adherence)
- When patients have poor drug absorption (vomiting or intestinal disease)
- When the TB drug supply is erratic (drug-outs)
- When the wrong TB therapy combinations, dose or treatment duration is prescribed
- When the TB drugs are of poor quality.
8-19 What is multidrug-resistant tuberculosis?
Multidrug-resistant tuberculosis (MDR-TB) is TB that is resistant to at least the two most powerful first-line anti-TB drugs: isoniazid (INH) and rifampicin (RMP). There are an estimated 650 000 patients with MDR-TB worldwide at any time.
Multidrug-resistant TB is TB that is resistant to isoniazid (INH) and rifampicin (RMP).
8-20 What is extensively drug-resistant tuberculosis?
Extensively drug-resistant (XDR-TB) is a form of TB which is resistant to at least four of the main anti-TB drugs: isoniazid (INH), rifampicin (RMP), any fluoroquinolones (e.g. ofloxacin or moxifloxacin) and to any of the injectable second-line drugs (amikacin, capreomycin or kanamycin).
The World Health Organization (WHO) states that about 9% of MDR-TB patients worldwide actually have XDR-TB, since in many sites advanced drug-susceptibility testing is not available.
8-21 Is drug-resistant tuberculosis more infectious than drug-susceptible tuberculosis?
DR-TB is spread from person to person as easily as drug-sensitive TB and by the same airborne route. In other words, DR-TB (MDR-TB and XDR-TB) is not more infectious; however, exposure to DR-TB may be prolonged for several reasons. In most cases the diagnosis of drug-resistance is delayed (by weeks or months). This is because many countries where TB is common lack molecular testing facilities for drug resistance. In addition patients with DR-TB take longer to smear conversion (i.e. remain smear positive and infectious for longer). They may also require more frequent and longer periods of hospitalisation resulting in greater exposure risk in healthcare facilities.
Drug-resistant tuberculosis is transmitted as easily as drug-susceptible tuberculosis and by the same airborne route.
Global tuberculosis control
8-22 What is the global tuberculosis programme?
The World Health Organization (WHO) has established the WHO Global TB Programme. This programme aims to advance universal access to TB prevention, care and control, guide the global response to threats, and promote innovation. Their core functions include:
- Provision of global leadership on TB
- Development of evidence-based policies, strategies and standards for TB prevention, care and control
- Provision of technical support and capacity building for Member States
- Monitoring the global TB situation measuring progress in TB care, control, and financing
- Shaping the TB research agenda with dissemination of valuable knowledge
- Facilitation of partnerships for TB action.
8-23 What is the 3I’s programme of tuberculosis control?
The World Health Organization (WHO) has developed the 3I’s strategy to help HIV and TB service providers to reduce the burden of TB among people living with HIV (PLWH).
- Intensified case finding aims to identify undiagnosed TB among PLWH, to reduce the delay between infection, diagnosis and treatment. Up to a quarter of individuals initiating antiretroviral treatment (ART) may have undiagnosed active TB, underlining the need for increased TB screening efforts.
- Isoniazid preventive therapy (IPT) for at least six months can reduce the TB disease burden in PLWH in whom active TB has been excluded. IPT is particularly useful for PLWH who are not yet on ART. IPT has been shown to be safe and well-tolerated.
- Infection control both within household and healthcare (clinic/hospital) settings is the third intervention recommended by WHO to reduce the spread of TB.
Tuberculosis infection prevention and control (TB-IPC)
8-24 What is the hierarchy of tuberculosis infection controls?
TB infection prevention and control includes a set of ranked interventions to reduce the risk of TB transmission, both in healthcare, community and household settings. These interventions are commonly known as the hierarchy of TB controls. They are ranked in order of importance:
- Administrative controls: to reduce the risk of TB exposure
- Environmental controls: to reduce the concentration of TB in the air and prevent spread
- Personal respiratory controls: additional risk reduction in high TB exposure settings.
These inter-connected control measures cut across programmes and disciplines, and require interaction and co-operation from multiple role-players in the healthcare context, including facility managers, healthcare workers, laboratory staff and patients/clients.
The hierarchy of tuberculosis infection controls are a set of ranked interventions to reduce the risk of transmission in healthcare, community and household settings.
8-25 Why is tuberculosis infection prevention and control needed in healthcare settings?
Poorly implemented or non-existent TB-IPC in healthcare settings can result in TB transmission to healthcare workers and patients alike. The 2005 outbreak of XDR-TB in Tugela Ferry, South Africa (52/53 patients who acquired XDR-TB died) should convince all healthcare workers of the need for TB-IPC. Recent research in South Africa has also reported very high rates of DR-TB (4–6 per 100 000 population) in healthcare workers compared with non-healthcare workers. In many low-resource settings, TB infection control measures are poorly implemented and occupational TB is common. Strengthening of TB-IPC is critical to prevent healthcare workers and patients from acquiring TB in the healthcare setting. However, ensuring that TB-IPC measures are adhered to requires involvement of all healthcare staff, as well as the co-operation of TB patients.
8-26 Who should ensure that tuberculosis infection prevention and control are implemented in healthcare settings?
It is usually the responsibility of the facility manager to ensure that the TB-IPC plan is implemented. The facility manager can delegate this responsibility to another member of staff, for example the IPC practitioner or the Occupational Health practitioner.
Every healthcare facility should have a named person responsible for implementing the tuberculosis infection control plan.
Administrative control measures
8-27 What is included in the administrative controls?
The administrative controls for TB infection control are placed at the top of the hierarchy. They are the most effective way to reduce the production of TB aerosols in the local environment. Early diagnosis of TB remains the most important intervention to reduce TB transmission. Several steps and role players are needed to ensure early diagnosis. These include:
- A patient-centred service
- Heightened clinical suspicion of TB
- Rapid specimen collection and processing
- Directed patient flows to avoid mixing of coughing adults with vulnerable patients (e.g. immunocompromised, young or elderly people)
- Implementation of strict cough triage and respiratory hygiene (separate coughing patients and provide them with surgical masks)
- Effective patient tracking and recall to commence treatment
- Treatment adherence by patients
- Active case-finding among household TB contacts (people who have been exposed to a TB case).
8-28 Who should be involved in implementing the administrative controls?
There are many people who should be directly involved in the implementation of administrative controls to prevent TB transmission in healthcare facilities, including:
- Facility management: to assign responsibility and accountability for TB-IPC; perform TB risk assessments with immediate corrective action when indicated; to develop, implement and evaluate the facility’s TB-IPC plan
- Laboratory services: to ensure timely processing and reporting of specimens
- Clinicians: to implement effective clinical management of TB patients (triage, isolation, treat promptly, discharge)
- The IPC practitioner: to train healthcare workers about TB-IPC, N95 respirators, supply appropriate signage for TB isolation areas, conduct TB surveillance and visit TB patients in wards
- The Occupational Health practitioner: to evaluate healthcare workers at risk for TB, monitor and report occupational TB statistics
- All roleplayers (everybody): to promote TB awareness and education for healthcare workers, patients, the community, encourage cough etiquette and respiratory hygiene and consider the possibility of TB as a diagnosis in all patients.
8-29 What is a facility tuberculosis risk assessment?
All healthcare facilities should assess and classify the risk of TB transmission in their setting once a year. The purpose of the risk assessment is to determine which of the components of the administrative, environmental and respiratory controls should be implemented. Risk classification also helps facilities decide if they need an occupational TB screening service. There are several tools available to assist facilities with the performance of TB risk assessments.
8-30 Which challenges do low-resource settings encounter with implementation of the administrative controls?
In low-resource settings there are multiple obstacles to full implementation of administrative controls for TB-IPC. Common areas where challenges are encountered include:
- Laboratory diagnosis of TB: there may be a lack of TB reference laboratories, limited TB diagnostic tests available, limited equipment and shortage of trained laboratory personnel, slow turnaround times (time between sputum sampling and return of laboratory results to healthcare practitioner) and inability to provide laboratory confirmation of drug-resistant TB.
- Infection Control and Occupational Health: many facilities lack IPC and/or Occupational Health-trained staff and services; there may be unfamiliarity with TB risk assessment protocols and insufficient capacity to train staff in TB-IPC.
- Facility: there may be a lack of leadership and accountability for implementation of TB-IPC plan; infrastructure problems may include lack of provision for separate waiting areas or triage of suspected TB; insufficient airborne isolation facilities and lack of cough rooms or cough booths for sputum sample production.
- Healthcare workers: may be unable to track TB patients when laboratory results are returned; may not have resources to perform active tracing of household contacts; may be reluctant to report occupational TB and may be unfamiliar with TB-IPC plans and the hierarchy of TB control measures.
- The community: may lack an awareness of how TB is transmitted and lack understanding of the principles of cough etiquette.
The administrative controls are the most important part of a tuberculosis control programme because they reduce exposure of susceptible individuals.
Environmental control measures
8-31 What is included in the environmental controls?
Environmental control measures for TB prevention are also sometimes referred to as engineering controls. They include the use of:
- Enhanced ventilation (natural)
- Negative pressure patient isolation rooms (mechanical ventilation)
- Ultraviolet germicidal irradiation (UVGI)
- High-efficiency particulate air (HEPA) filtration systems.
The aim of the environmental controls is to remove, replace or ‘clean’ contaminated air. By reducing or diluting (with fresh air) the concentration of TB bacilli in the air, the potential for TB transmission is decreased.
The aim of the environmental controls is to remove, replace, dilute or ‘clean’ contaminated air.
8-32 What is natural ventilation?
Ventilation is the provision of fresh air to a room or building. Natural ventilation is the process of supplying and removing air through an indoor space without the use of mechanical systems. Movement of air occurs on its own because of differences in temperature or pressure between locations. Natural ventilation is the preferred method of ventilation in low-resource settings and has many advantages over mechanical ventilation (see below). In its simplest form, natural ventilation can be achieved by opening windows and doors in healthcare facilities. Natural draughts (movement) of air replaces stale, stagnant and/or pathogen-contaminated air (TB or respiratory viruses) with fresh air from the outside environment. Fans can also be used to help direct the movement of air in a room.
The direction of air flow should be considered when setting up consultation rooms. The healthcare worker should sit closest to the fresh air source and the patient closest to the air outlet. This ensures that any air with potential pathogens (e.g. TB) is removed away from the healthcare worker.
Figure 8-1: Recommended layout of examination room for patients with TB or suspected TB
Natural ventilation is the preferred method of ventilation in low-resource settings.
8-33 What are the advantages of natural ventilation?
Natural ventilation requires no equipment, no electricity and no maintenance. In addition it does not generate any noise and in hot climates can be used to provide free cooling of the environment.
8-34 What are the disadvantages of natural ventilation?
The use of natural ventilation is dependent on the correct climate conditions (including wind direction, force and humidity). Natural ventilation may cause discomfort for patients as it often results in cooling of the environment. Another disadvantage is that staff and patients can close windows and doors thereby preventing air replacement by natural means.
8-35 What is mechanical ventilation?
Mechanical ventilation (or controlled ventilation) is the process of supplying and removing air through an indoor space with the use of mechanical systems. Mechanical ventilation is used in settings where a high risk of TB exposure is expected, for example airborne isolation rooms and TB clinics. There are two types of mechanical ventilation: local exhaust ventilation and general ventilation.
8-36 What is local exhaust ventilation?
Examples of local exhaust ventilation include window-mounted extractor fans and ceiling-mounted ‘whirlybirds’. These devices extract air from a small, confined space, e.g. cough room or isolation room and usually remove (exhaust) the air directly to the outside air. These devices (although more expensive than natural ventilation) are generally much cheaper, require less technical expertise to install and need less maintenance than general ventilation systems.
8-37 What is general ventilation?
General ventilation is usually achieved by the use of air-handling units that can control direction and rate of air movement over larger areas, e.g. waiting areas, TB wards. Air-handling units are effective in preventing TB transmission by: removing contaminated air; diluting TB by introduction of fresh air and controlling the movement of potentially contaminated air within a space. Air handling units used for reduction of TB transmission should achieve at least 6–12 air changes per hour. This means that the entire volume of air in the room/space should be removed and replaced with fresh air at least six times per hour. As with local exhaust ventilation, removed air is directed out into the environment. In situations where that air may re-enter a room or building, additional methods like filtration or ultraviolet radiation is needed to ‘clean’ the air. In most cases though, if the air is exhausted to the outside, it is rapidly diluted and no additional decontamination is required.
Mechanical or natural ventilation for reduction of TB transmission should achieve at least 6–12 air changes per hour.
8-38 What is negative pressure ventilation?
Negative pressure ventilation is used to prevent movement of contaminated air into areas with susceptible people. It is used in airborne isolation rooms or facilities where patients with TB, measles or varicella (chickenpox) infection are admitted. In this situation the amount of air extracted (removed) from the room is greater than the air supplied. To ensure that negative pressure is maintained, all windows and doors should be closed. The air extracted from contaminated areas should ideally be released into the outside atmosphere, and not re-circulated to other areas of the healthcare facility.
8-39 What is a cough room?
A cough room or cough booth is a small confined space where a patient goes to produce a sputum sample. Coughing produces large amounts of infectious TB droplet nuclei which may remain suspended in the air for prolonged periods of time. For this reason, a designated area with good ventilation is needed to reduce the possibility of cross-infection in TB facilities. In addition to good ventilation, the ideal cough room should be situated away from clinical areas and patient waiting rooms, and should include handwashing facilities.
8-40 What other features should be included in the design of tuberculosis isolation facilities?
A single negative-pressure room (with en suite bathroom facilities) is preferred for isolation of newly diagnosed TB patients, especially if drug-resistant TB is suspected. In most low-resource settings, single room isolation facilities are limited, necessitating cohorting of patients. A cohort is a group of patients with the same infectious pathogen that are nursed together. For wards or patient bays that cohort TB patients, the following features are recommended: Bed spacing should be at least
- 2.5 metres (measured from the centre of one bed to the centre of the next bed).
- Each bed should have individual curtains, so that these can be closed to contain the spread of TB droplet nuclei during coughing or aerosol-generating procedures. These must be changed with the bed linen change on discharge of each patient.
- Surfaces should be easy to clean and keep dry.
- Sufficient handwash basins should be available to staff and patients.
- The room/ward should be well-ventilated (either naturally or mechanically) to achieve between six and 12 air changes per hour.
- Safe outdoor spaces for relaxation and visiting with relatives should be provided (e.g. central courtyards or verandas).
8-41 What is ultraviolet germicidal irradiation (UVGI)?
Ultraviolet germicidal irradiation (UVGI) can be used in addition to negative-pressure ventilation, in high-risk areas. Ultraviolet light at a specific wavelength (254 nanometres) kills TB bacilli (also viruses and other bacteria) that are suspended in the air. UVGI alters the DNA of the TB bacillus, leading to death of the bacillus given sufficient time and intensity of exposure to UV light.
The effectiveness of UVGI for TB prevention in low-resource settings is dependent on several factors:
- Regular monitoring and servicing of the UVGI lights are required
- The tubes require replacement after a certain amount of hours (consult suppliers)
- High levels of humidity may interfere with the UVGI
- Excessive amounts of dust settling on the light tubes also reduce effectiveness
- Air circulation is required to bring the TB bacilli within close range of light tubes
- Skin damage, skin cancers and retinal damage are possible following prolonged exposure to improperly maintained UVGI.
8-42 Which challenges do low-resource settings encounter with implementation of the environmental controls?
Important challenges include:
- Lack of technical expertise: with a major shortage of skilled professionals and technicians for facility design, architectural planning, ventilation engineering and supply, maintenance of UVGI.
- Lack of knowledge: facility managers and healthcare workers may be unaware of the need for regular servicing and maintenance of ventilation systems and UVGI. This may give rise to a false sense of security, where the visible measures for environmental control may in fact be non-functional.
- Unsuitable facility design: many facilities do not have provision for patient separation, isolation rooms and cough rooms. New building or refurbishment planning projects may not take TB-IPC requirements into account.
- Financial: the provision of single room, en suite, negative pressure ventilation areas may be unaffordable in most low-resource settings.
Respiratory protection control measures
8-43 What is included in the respiratory controls?
The respiratory controls (also known as personal respiratory protection) are intended to provide additional protection in high-risk circumstances. It is important to remember that the administrative and environmental controls are far more effective in reducing TB transmission risk. Respiratory protection (if used correctly) can give additional benefit, especially for exposures to drug-resistant TB.
8-44 What is the difference between a face cover, a surgical mask and a N95 respirator?
A face cover is any piece of personal protective equipment designed to cover the nose and mouth of the wearer, e.g. surgical masks or N95 respirators.
To prevent release of TB bacilli when coughing, patients can be asked to use a disposable tissue or handkerchief to cover their cough or to wear a surgical mask. Although a surgical mask is effective in containing respiratory droplets, its filter efficiency is poor and short-lived. For this reason, surgical masks are not recommended for respiratory protection of healthcare workers.
N95 respirators should be worn when within 3 metres of an infectious TB source case. These respirators have very high filtering efficiency, preventing inhalation of over 95% of particulate aerosols. Particles from 0.1–10 microns in size are filtered out, including TB droplet nuclei which are about 2–5 microns in size.
N95 respirators should be worn by healthcare workers when in close contact with infectious tuberculosis patients.
8-45 What is a N95 respirator fit-test?
In order to be effective, it is essential that N95 respirators are properly fitted to the size and shape of an individual healthcare worker’s face. N95 respirators are available in different sizes and styles, e.g. cone- or cup-shaped; duckbill-shaped and others with built-in expiratory valves. This is to maximise the chance of finding a respirator that can provide a tight seal on the wearer’s face. Excessive facial hair or beards will prevent a proper seal being formed.
All healthcare workers should be fit-tested by an expert prior to using a N95 respirator. This involves formal testing of a particular size/style respirator’s ability to protect the wearer from inhaling particulate aerosols. At the time of fit-testing, staff should also be trained in the correct method of donning (putting on) and doffing (removing) the respirator.
Figure 8-2: Face covers for TB patients and healthcare workers
N95 respirators are only effective at reducing risk of tuberculosis infection if worn correctly, consistently and stored appropriately.
8-46 How should N95 respirators be used and cared for?
In low-resource settings, N95 respirators are often re-used intermittently for up to one week or to a maximum of eight hours of use and then discarded. The proper care of the respirator is critical to ensuring its ongoing effectiveness. It should be stored dry (in an envelope marked with the healthcare worker’s name) because moisture reduces the filtering ability of the respirator. In addition, respirators should not be folded, crushed or torn. Respirators should be inspected for damage or surface contamination (by blood or body fluids) after every use.
If surgical masks are used by healthcare workers, these should be discarded immediately after use, as their filtering efficiency is limited to 10 to 15 minutes.
8-47 When should patients with tuberculosis wear face covers?
Patients with suspected TB or confirmed TB who are not yet sputum TB culture-negative should wear surgical masks in the following situations:
- During transportation between healthcare facilities
- While being moved about within a healthcare facility (e.g. going for X-rays)
- When present in patient waiting areas
- When other persons or patients are present in the room.
It is only necessary for TB patients to wear a face cover when in the presence of other people in a closed or a poorly ventilated environment. N95 respirators should never be used on patients as they are primarily designed to filter the air and can worsen shortness of breath in patients with lung damage.
8-48 Which challenges do low-resource settings encounter with implementation of the respiratory controls?
Important challenges include:
- Unavailability of personal protective equipment: N95 respirators are more expensive than surgical masks and may be unavailable or difficult to obtain; alternatively only selected shapes and sizes of respirators may be made available to staff.
- Lack of equipment and expertise to perform N95 respirator fit-testing: the N95 respirator fit-test kit is costly and the test solutions need to be replaced when used or expired; facilities may lack staff with the expertise and time to conduct the fit-testing assessments.
- Lack of staff adherence to respiratory controls: even when readily available, some staff members may refuse to use N95 respirators.
- Lack of understanding: staff may inappropriately insist that patients wear N95 respirators. This causes discomfort for patients, and takes away respirators that should be used for staff protection.
Healthcare worker adherence to tuberculosis control measures
8-49 How high is the risk to healthcare workers of occupational tuberculosis?
Rates of DR-TB (4–6 times higher than risk to the general population) have been reported in South African healthcare workers. In the group of healthcare workers described by this study, very few had been previously treated for TB. This implies that they were primarily infected with a DR-TB strain. The increased risk for development of TB (and DR-TB) among healthcare workers reflects substantial and unrecognised TB exposures in the workplace.
The increased risk for development of TB in healthcare workers reflects substantial and unrecognised TB exposures in the workplace.
8-50 What are the reasons for non-adherence to tuberculosis infection prevention and control measures?
Even though TB infection control policies and control measures are available, many healthcare workers disregard their risk of TB acquisition. Some of the reasons given by healthcare workers for not implementing TB infection control measures were:
- Not being bothered ‘very much’ by catching TB
- Feeling less susceptible to TB
- Fear of stigmatisation
- Discomfort from wearing N95 respirators.
TB infection control programmes need to take into consideration and address the reasons for non-compliance with intervention measures.
8-51 How can healthcare workers be encouraged to implement tuberculosis infection prevention and control measures?
This is a complex problem and requires actions at multiple levels of the healthcare system. Some suggestions to improve healthcare worker compliance with TB infection control programmes include:
- National prioritisation of TB-IPC: endorsement of TB-IPC as a top priority by governments/ departments/ministries of health; mandated training of healthcare workers in TB-IPC; inclusion of TB-IPC in all undergraduate health science curricula.
- Institutional prioritisation of TB-IPC: there should be commitment from the healthcare facility manager to implement the facility TB-IPC plan; mandatory in-service training in TB-IPC for all healthcare workers; mandatory N95 respirator fit-testing of all clinical staff; annual TB risk assessments and sharing of results with staff and regular occupational TB awareness campaigns.
- Social proof and individual accountability: healthcare worker ‘champions’ for TB-IPC should be identified at each facility; senior clinical staff should ‘set the example’ for junior staff and facilities should consider the use of incentives and/or disincentives for adherence and non-adherence to TB-IPC controls.
Occupational health services for tuberculosis
8-52 When should healthcare workers be investigated for tuberculosis?
In some settings, healthcare workers may be offered a baseline (pre-placement) TB screening chest X-ray or annual blood tests to identify new latent TB infections (interferon gamma release assays – IGRA). Identification of new LTBI gives the opportunity to provide isoniazid (INH) prophylaxis where needed.
Any healthcare workers with possible symptoms of TB disease should be promptly referred for TB screening at their nearest staff clinic. Staff working in high-risk areas for TB should be encouraged to determine their HIV status at regular intervals. Healthcare workers with known underlying immune-compromise (e.g. HIV, diabetes, steroid therapy), should be encouraged to disclose these conditions. This will allow occupational health services or facility managers to deploy such staff members in lower TB infection risk areas. Staff should also be discouraged from smoking, which may increase their risk of acquiring TB.
Symptom screening is another way to improve identification of staff with undiagnosed TB. Healthcare workers (in medium- to high-risk TB exposure settings) should undergo intermittent symptom screening with referral for investigation if any suspicion of TB disease.
8-53 How should healthcare workers be investigated for tuberculosis?
Healthcare workers with possible symptoms of TB should be referred to their nearest occupational health service for the following investigations:
- History and full clinical examination
- Chest X-ray
- At least two consecutive early morning sputum samples for TB microscopy, culture and sensitivity and/or
- Molecular testing (GeneXpert®) where available
- Voluntary counselling and testing for HIV (HIV rapid or ELISA)
- Other investigations (as determined by the clinical examination).
8-54 What surveillance and reporting are required for occupational tuberculosis?
In most countries, monitoring for workplace or occupational infection is required by law. Healthcare facility managers should be familiar with the requirements for healthcare worker protection. Each facility should conduct annual TB risk assessments and implement appropriate TB control measures. In many countries surveillance and reporting of TB infection and disease among healthcare workers are incomplete. For this reason, occupational TB is often not perceived to be a real threat to healthcare workers in countries where TB is most common.
Tuberculosis prevention in the community
8-55 What should newly diagnosed patients be told about preventing household spread of tuberculosis?
Wherever possible, a patient treated for TB should sleep in a separate room to other household members, particularly children under five years of age. The door to their room should be closed and the windows opened. All surfaces in the room should be kept clean and dust-free to avoid re-aerosolisation of TB droplets.
Good cough etiquette should be practised at all times: patients should use tissues or a handkerchief to cover their mouth and nose when sneezing or coughing; used tissues should be discarded immediately into a plastic bag, although a handkerchief may be re-used if good hand hygiene is performed. Hands should be washed with soap and water or cleaned with alcohol handrub. Caregivers should wash hands or use alcohol handrub immediately after each patient contact. If the patient goes outside, it is not necessary to wear a mask or face cover.
Discourage visitors while the patient remains infectious. In cases of drug-susceptible TB, the infectiousness of the TB source case will decline dramatically within one to two weeks of starting treatment (assuming good treatment adherence). For this reason, it is usually not necessary for caregivers to wear a surgical mask or face cover when nursing the patient beyond two weeks, unless there is poor treatment adherence or suspected drug-resistant TB.
8-56 Which other settings pose a risk for tuberculosis transmission?
Outside of the traditional healthcare facility environment, there are several other settings where transmission of TB can occur, e.g. home-based care, long-term care facilities, correctional facilities (prisons), shelters for the homeless and emergency medical (ambulance) services. In all such settings where patients with TB disease may receive care, a TB infection control risk assessment should be performed and a TB-IPC plan implemented.
Case study 1
A three-month-old baby is admitted to hospital with coughing and severe shortness of breath. Tuberculosis is strongly suspected but the baby has no household TB contacts. The baby was born prematurely and spent his first three weeks of life in the Kangaroo Mother Care (KMC) ward. His mother remembers sharing a room with a lady who looked sick and coughed continuously. Doctors find the potential adult source/index case and confirm that she has smear-positive TB. Her M. tuberculosis culture strain is identical to the baby’s strain. A contact investigation is started for babies who shared the adult TB source case’s room in the KMC ward. Four of the eight babies (50%) have already been treated for TB. None had household TB contacts and therefore most likely acquired TB in the KMC ward after birth.
1. What factors make the transmission of tuberculosis more likely in this setting?
Patients at extremes of age (i.e. newborn babies) are very vulnerable to developing TB disease after being infected with TB (latent TB). The cramped and poorly ventilated environment in most Kangaroo Mother Care wards also increases the risk of TB exposure.
2. How could this situation have been prevented?
As part of the administrative controls, healthcare workers should consider the possibility of TB disease in all patients. A simple TB symptom screening checklist administered before admitting mothers to the kangaroo ward could have identified the TB source case mother. In addition, she should have been referred for TB investigations after staff had noticed her coughing in the ward.
3. Why are neonatal and paediatric wards a medium- to high-risk area for tuberculosis exposure?
The greatest burden of TB disease occurs in young adults, including women of child-bearing age. In many TB-endemic countries, HIV infection is also common. People living with HIV are at very high risk of TB disease (up to 10% risk of TB disease each year). Since parents often remain in hospital for prolonged periods with their sick children, they pose a great risk for TB transmission (if they have undiagnosed active TB disease).
Case study 2
AB is a 25-year-old male college student who comes to your clinic for evaluation of fever and cough. He has been coughing for about six weeks. He has consulted the college’s student clinic previously and was given a course of antibiotics, without improvement. He continued to have fever especially at night with sweats and chills. His appetite is poor and he has lost 5 kilograms in the last month.
1. What features should alert the physician to a possible diagnosis of pulmonary TB?
The presence of cough for more than two weeks along with fever, night sweats, poor appetite and weight loss are signs and symptoms suggestive of pulmonary TB. The lack of improvement after a course of antibiotics is also an important clue to the possibility of TB.
2. What investigations or tests should the healthcare worker send from this patient?
The student should produce at least two sputum samples to be sent for TB sputum smear microscopy and culture. If available, a chest X-ray may be helpful as additional evidence of TB.
3. The sputum test is smear positive for acid-fast bacilli (3+ AFB-positive) and the patient is started on anti-TB medication. What advice should be given to the patient regarding medication?
The importance of adherence to medication for the full duration of treatment must be emphasised. He should be made aware that even if he starts to feel better he should continue to take the medications for a full six months. Excellent treatment adherence may reduce the risk of relapse and development of drug-resistant TB.
4. What advice will you give the student regarding return to college?
The student should report his illness to the college’s student clinic and wait to return to classes until his repeat sputum tests are smear- and culture-negative for TB. Contact tracing should be done to identify persons exposed to the TB smear-positive student. If the student stays in shared accommodation (e.g. a college dormitory) he should be allowed to go home. His roommates should be screened for TB.
Case study 3
Mrs FG is a 35-year-old lady who has just delivered her second child. She was diagnosed with smear-positive pulmonary TB during the last month of her pregnancy and was put on anti-TB medicines. She, her husband, first children and in-laws live in the same household.
1. Mrs FG is really worried about passing the TB to her new baby. What can be done to prevent TB transmission to the baby?
The concern of transmitting TB to her baby is very valid. Children with TB are usually infected by adults around them with untreated or undiagnosed TB. Mrs FG should submit a repeat sample for sputum microscopy and culture at the end of the second month of treatment. She must wear a surgical mask while indoors and practise good cough etiquette until she is sputum-smear-negative. In the meantime she may care and breastfeed her baby as normal. The baby will need to be followed up at the clinic regularly in the first six months of life. The baby should receive INH prophylaxis if the mother is still infectious.
2. Who among the household members need to be screened for contact tracing purposes?
All household members should be screened, especially children under the age of five and people who share a room with the index case (the patient with pulmonary TB).
3. What advice should be given to households with an infectious TB patient?
Wherever possible, a patient treated for TB should sleep in a separate room to other household members, particularly children under five years of age. The door to their room should be closed and the windows opened. All surfaces in the room should be kept clean and dust-free.
Patients should use tissues or a handkerchief to cover their mouth and nose when sneezing or coughing. Used tissues should be discarded immediately into a plastic bag. Hands should be washed with soap and water. If the patient goes outside, it is not necessary to wear a mask/face-cover, but the person should still maintain good cough etiquette. Discourage visitors while the patient remains infectious. Family members may share crockery and cutlery. The household members should help in the treatment of the TB by being supportive treatment partners.
In cases of drug-susceptible TB, the infectiousness of the TB source case will decline dramatically within one to two weeks of starting treatment (assuming good treatment adherence). For this reason, it is usually not necessary for caregivers to wear a surgical mask/face-cover when nursing the patient beyond two weeks, unless there is poor treatment adherence or suspected drug-resistant TB.
Case study 4
Mr XY, a 40-year homeless man, is brought to the emergency unit because he is coughing up blood (haemoptysis). He was started on treatment for pulmonary TB eight months ago, but defaulted treatment after just two months. The doctor admitting him is concerned about the possibility of drug-resistant TB.
1. What immediate actions should the doctor take?
Mr XY should be placed in a single room with door closed or in an isolation cubicle with the curtains drawn. Any healthcare worker attending to him should wear appropriate personal protective equipment (i.e. N95 respirator, apron, gloves and eye shields, since he is coughing up blood). An airborne-precautions sign should be placed at the door or on the curtains, to make all staff aware of the risk.
2. Once the bleeding has stopped, the doctor wants to get a sputum sample from the patient to send for smear microscopy, culture and GeneXpert® testing. Where should the patient go to produce the sputum sample?
If the patient is too unwell to leave his bed, he can produce a sputum sample with the bed curtains drawn. The curtains should remain closed for at least 15 minutes after the sputum sample is taken.
If he can walk, he should put on a surgical mask and walk to a well-ventilated outdoor area or to a cough room (if available). Patients should never be sent to the bathroom/toilet to produce sputum.
He should wash his hands well with soap and water after producing the sputum sample.
3. The patient is confirmed to have drug-resistant TB and is admitted for several weeks on the medical wards in an isolation cubicle. Despite the IPC practitioner’s best efforts, many ward staff are reluctant to wear their personal protective equipment. What are possible reasons behind these feelings of resistance?
Even though TB-IPC policies and control measures are available, many healthcare workers disregard their risk of acquiring TB. It has been shown (especially in countries with high TB burden) that healthcare workers are at increased risk of TB disease. Some of the reasons given for non-compliance with TB-IPC measures are: feeling less susceptible to TB, fear of stigmatisation and the discomfort of wearing N95 respirators. The IPC practitioner and hospital management should actively address the reasons for non-compliance with intervention measures.